Exhaust backfiring

[rich weyand]

I'm not talking about the idle mixture. The carb has four circuits, the idle circuit, the cruise (primary) circuit, the power circuit, and the secondary circuit. The middle two of these are richer than a cob or you wouldn't be getting such terrible gas mileage. The adjustments required are made, according to the manual, by modifications to the PRIMARY METERING JET. SECONDARY METERING PLATE, PUMP DISCHARGE NOZZLE, PRIMARY POWER VALVE, SECONDARY DIAPHRAGM SPRING. These modifications are most easily done with an accurate A/FR meter.